This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2000-284188, filed Sep. 19, 2000; No. 2001-003901, filed Jan. 11, 2001; and No. 2001-248120, filed Aug. 17, 2001, the entire contents of all of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a silver halide photographic emulsion and a silver halide photographic lightsensitive material using the same. More specifically, it relates to a silver halide photographic emulsion of a high sensitivity and a hard gradation, and a silver halide photographic lightsensitive material using the same.
2. Description of the Related Art
The use of tabular silver halide grains (to be referred to as xe2x80x9ctabular grainsxe2x80x9d hereinafter) to obtain a high-speed silver halide photographic light-sensitive material is well known to those skilled in the art. Methods of sensitizing these tabular grains by using epitaxial junctions are disclosed in Jpn. Pat. Appln. KOKAI Publication No. (hereinafter referred to as JP-A-)58-108526 and JP-A-59-133540. Also, applications to thinner tabular grains or to tabular grains having larger equivalent-circle diameters are disclosed in JP-A""s-8-69069, 8-101472, 8-101474, 8-101475, 8-171162, 8-171163, 8-101473, 8-101476, 9-211762, and 9-211763, and U.S. Pat. Nos. 5,612,176, 5,614,359, 5,629,144, 5,631,126, 5,691,127, and 5,726,007. However, in an epitaxial sensitizing method of using silver chloride as a main composing element, although high sensitivity can be obtained, there is a problem that gradation does not easily become hard. This prevents the epitaxial sensitizing method and the epitaxial grains or prior arts from using it multipurposly in a lightsensitive material for general photographing.
An object of the present invention is to provide a silver halide photographic emulsion satisfying a high sensitivity and a hard gradation of epitaxial tabular grains simultaneously, and a silver halide photographic lightsensitive material using the same.
The inventors of the present invention considered the problem that the gradation is not hard as being caused by the facts that epitaxial protrusion portions of a conventional epitaxial emulsion have a low silver iodide content, and that the halogen compositions of the epitaxial protrusion portions become non-uniform between the epitaxial protrusion portions when one tries to increase the silver iodide content of the epitaxial protrusion portions. Then, the inventors made researches to improve them. As a result, the inventors found that it is possible to increase the silver iodide content of the epitaxial protrusion portions by adding a silver iodide ultrafine grain emulsion prepared just before the addition thereof at the time of forming the epitaxial protrusion portions, and thereby the halogen compositions of the epitaxial protrusion portions become uniform in each grain and between the grains. As a result, the inventors found that it is possible to obtain a photographic property of a high sensitivity and a hard gradation, and completed the present invention.
Namely, the above object has been achieved by the following means (1)-(10).
(1) A silver halide photographic emulsion, wherein at least 70% of the total projected area of silver halide grains contained therein is occupied by silver bromochloroiodide hexagonal epitaxial tabular grains each having (111) faces as main planes and an epitaxial protrusion portion, wherein the epitaxial protrusion portion exists on at least one apex portion of the hexagon, and, when an average silver chloride content of the epitaxial protrusion portions of all the grains having the epitaxial protrusion portion is expressed as CL mol %, a silver chloride content of each epitaxial protrusion portion of each grain falls within the range of 0.7 CL to 1.3 CL.
(2) The silver halide photographic emulsion according to item (1), wherein the silver chloride content of each epitaxial protrusion portion of each grain falls within the range of 0.8 CL to 1.2 CL.
(3) A silver halide photographic emulsion, wherein at least 70% of the total projected area of silver halide grains contained therein is occupied by silver bromochloroiodide hexagonal epitaxial tabular grains each having (111) faces as main planes and an epitaxial protrusion portion, wherein the epitaxial protrusion portion exists on at least one apex portion of the hexagon, and, when an average silver iodide content of the epitaxial protrusion portions of all the grains having the epitaxial protrusion portion is expressed as I mol %, a silver iodide content of each epitaxial protrusion portion of each grain falls within the range of 0.7I to 1.3I.
(4) The silver halide photographic emulsion according to item (3), wherein the silver iodide content of each epitaxial protrusion portion of each grain falls within the range of 0.8I to 1.2I.
(5) The silver halide photographic emulsion according to any one of items (1) to (4), wherein each epitaxial protrusion portion of each grain contains silver iodide, and the silver iodide content of each epitaxial protrusion portion of each grain is at least 10 mol %.
(6) The silver halide photographic emulsion according to item (5), wherein a silver iodide content of each epitaxial protrusion portion of each grain is at least 20 mol %.
(7) A silver halide photographic lightsensitive material, comprising a lightsensitive layer on a support, the lightsensitive layer containing the silver halide photographic emulsion according to any one of above items (1) to (6).
(8) A method of preparing the silver halide photographic emulsion according to any one of above items (1) to (6), wherein the epitaxial protrusion portion are formed by adding a silver iodide ultrafine grain emulsion prepared just before being added.
(9) The method of manufacturing the silver halide photographic emulsion according to above item (8), wherein the average equivalent circle diameter of the silver iodide ultrafine grain emulsion is 0.02 xcexcm or less.
(10) The method of manufacturing the silver halide photographic emulsion according to above item (8), wherein the average equivalent circle diameter of the silver iodide ultrafine grain emulsion is 0.01 xcexcm or less.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.